Lysis chemistry leads to shorter enrichment times for new assays – 3M

The 3M Molecular Detection Assay 2 – Listeria and 3M Molecular Detection Assay 2 – ​Listeria monocytogenes are based on the same technologies used in the previous model – isothermal DNA amplification and bioluminescence detection.

The assays use a workflow that is 30% faster than first generation assays thanks to new lysis chemistry that uses proprietary 3M nanotechnology and features a color-change indicator for increased control during assay processing.

Assay development​

John David, global marketing supervisor with 3M Food Safety, said the assay chemistry eliminates certain steps and improves workflow.

“For example, the 3M Molecular Detection Assay 2 tests use a 3M nanotechnology and liquid-phase chelating technology that replaces the lysis tube resin used in the first generation assay. These new assays now use a color indicator that changes automatically, in response to customer feedback," ​he told FoodQualityNews.

“This lysis chemistry used in the next-generation 3M Molecular Detection Assays enables the tests to deliver shorter enrichment times, and makes for a streamlined protocol with fewer steps. The color-change indicator also provides customers with an additional process control to help them know when to proceed to the next step.”​

Applicable to environmental samples and food types (dairy products, ready-to-eat and raw meats, fish and seafood, fruits and vegetables) and using a standard enrichment medium, the next generation assays provide a faster time-to-result after 24 hours of enrichment.

David said customers want to be confident that a pathogen detection system will work with specific food product types, and typically conduct in-house evaluations to ensure the method’s performance meet expectations.

“After 24 hours of enrichment, it takes 35 minutes to process 96 samples and start the instrument run. Positive results are identified in 15 minutes, so customers can start seeing positive results in less than one hour after the enrichment,” ​he said.

“Negative results are identified at the end of the 75-minute instrument run. Total time to negative results, therefore, is less than two hours after enrichment.”​

Changing generations​

First and second generation assays can be run simultaneously using the same 3M Molecular Detection Instrument.

To use the assays on existing instrument, customers need to download and install a free software upgrade.

This software has a redesigned user interface and features that allow for more efficient data entry and improved administrative control.

“We have made the transition from the current 3M Molecular Detection Assays to the next-generation tests as seamless as possible by using the same Demi Fraser Broth enrichment medium as in the first-generation tests, as well as using the same instrument,” ​said David. ​

“We understand that some customers will take longer than others to phase over to the new assays, and during that time customers can run the first-generation and next-generation assays together in the 3M Molecular Detection Instrument at the same time.”  ​

The next 3M Molecular Detection Assay 2 test will be for Salmonella, and will use the same protocol.

3M is pursuing AOAC validations for the Listeria and Listeria monocytogenes assays and expects to receive AOAC Performance Tested Methods (PTM) for both assays this year. 

It also expects to receive AOAC Official Method of Analysis (OMA) validation in early 2016. 

The firm said it will then seek AOAC PTM and AOAC OMA approval for the Salmonella assays.